This is a heavily modded LaFrance M16K as the Rocky Mountain Arms "Patriot Pistol" did not work in full auto.
S&W 629 Hunter
Snake Plissken (Kurt Russell) carries two S&W 629 Hunter .44 Magnum revolvers as his sidearms of choice.
These guns are S&W Performance Center modified, and were equipped with Aimpoint red dot scopes as well.
AC556
As used by Cuervo Jones, It is the stainless steel edition but with a polymer Choate Stock and mounted scope which in real life is used by the Royal Bermudan Military. Cuervo Jones uses it to attempt to snipe Snake, but Utopia tackles Jones, making him miss. Snake later takes this gun from Cuervo to replace his Coreburner.
FN FAL
The USPF guards carry FN FAL battle rifles with Cobray 37mm Launchers mounted on them. The FN FAL were a mix of semi-auto Springfield Armory SAR-48's and selective fire LaFrance Specialties FAL's with Cobray CM203 launchers and a custom flash hider. - Phoenixent
Heckler & Koch HK93A3
The Presidents daughter Utopia had a HK93A3 with bipod on board the plane. - Phoenixent
Heckler & Koch MP5
Seen in the hands of various gang members, including Cuervo Jones' army and the Saigon Shadows.
Converted Heckler & Koch SP89
During the air raid on Cuervo Jones, Snake has a custom HK SP89 with a stainless steel receiver. The same one used by Dennis Hopper in the movie Speed. - Phoenixent Hershe also has a garden variety MP5K with a black receiver.
Heckler & Koch HK94
The HK94, a civilian, long-barrel semiauto version of the MP5, is seen in the hands of various gang members.
AKM
The hippie surfer ('Pipeline', Peter Fonda) carries this weapon when he meets Snake Plissken on the beach. Seen in the hands of various gang members in L.A. (AKM variants being very common)
'Galil'
7.62x39mm AK derivates with Galil-like foregrips and stocks are seen at various points in the movie. The banana-curved magazine gives it away as the only Galil- or Galil-based weapons ever made are chambered for 5.56x45 or 7.62x51mm and do not have these extremely curved magazines.
M16
Seen in the hands of various gang members.
M1 Garand
Seen in the hands of various gang members, including the members of Cuervo Jones' gang.
Springfield M1903
Seen in the hands of Cuervo Jones' gang members.
Heckler & Koch G3
Seen in the hands of various gang members.
Mauser Karabiner 98k
Seen in the hands of Cuervo Jones' gang members.
Ruger Mini 14 Rifle
The Ruger Mini-14 is seen on at least one occasion in a gang member's hands.
Micro Uzi
Micro Uzis make various appearances throughout the movie. They are mostly used by criminal gangs e.g the Korean Dragons.
Seen in the pistol holster of the Surgeon-General of Beverly Hills (Bruce Campbell). Snake later takes this pistol from him after shooting him with a small blowdart.
Net gun
The Surgeon General's caped staff use a net gun to capture Snake.
Magnum Research Desert Eagle
Snake Plissken takes Map to the Stars Eddie's .50AE Desert Eagle.
Ruger P90
Cuervo Jones carries a Ruger P90 throughout the film.
Cuervo Jones (George Corraface) attempts to shoot down Pliskin's helicopter with an AT4 rocket launcher. It is famously seen from the front unloaded for about a second, then suddenly fires a missile.
Street Sweeper
A gang member is seen holding a Street Sweeper towards the air and later shooting it with an angled foregrip.
MAC-10
A gang member holds a MAC-10 while escorting Snake to the basketball field.
Seecamp 32
Hershe carries a Seecamp 32ACP pistol between her legs.
SPAS-12
A Franchi SPAS-12 is seen in the hands of a gang member at the Happy Kingdom.